Deep-Dive Guides · Nucleic Acids
Nucleic Acids — the complete deep dive
Nucleic-acid chemistry is built from a very small parts list: five bases, two sugars, a phosphate, one kind of glycosidic bond, and one kind of phosphodiester backbone.
Free extract — the opening section of the guide, in full.
0. How to use this guide — the parts list
A nucleic acid is a polymer of nucleotides. Each nucleotide has three parts, and every question ultimately probes one of them or how they assemble:
| Part | Options | What it controls |
|---|---|---|
| Nitrogenous base | purines (A, G) & pyrimidines (C, T in DNA / U in RNA) | information content; base pairing (A–T/U, G–C) |
| Pentose sugar | 2′-deoxyribose (DNA) vs ribose (RNA) | chemical stability; the 2′-OH distinguishes RNA |
| Phosphate | on the 5′ (or 3′) hydroxyl | the negatively charged backbone; directionality (5′→3′) |
The build-up (memorise the ladder): base + sugar (β-N-glycosidic bond) = nucleoside; nucleoside + phosphate (ester) = nucleotide; nucleotides joined by 3′,5′-phosphodiester bonds = a polynucleotide strand; two antiparallel complementary strands = the double helix. Four questions answer most problems: (1) purine or pyrimidine? (2) ribo or deoxyribo? (3) how many H-bonds in the pair (A–T = 2, G–C = 3)? (4) what does the base composition/salt do to Tm?
Read the rest of this guide
The remaining 11 sections — Bases, nucleosides & nucleotides, The sugar–phosphate backbone, Base pairing & Chargaff's rules, The double helix, forms & stability (Tm) and more — are part of ChemVidya Full Access, along with the other guides, the books, the study notes and 6,000+ practice questions with worked solutions.